JP3586337B2 - Fault diagnosis method for vehicle mobility control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a failure diagnosis method for diagnosing a failure of an actual motion state quantity sensor used for feedback control of a vehicle behavior.
[0002]
[Prior art]
Feedback control is performed so that the target motion state quantity calculated according to the driver's operation amount or the vehicle motion state quantity (vehicle speed, yaw rate, lateral acceleration, etc.) and the actual motion state quantity detected by the actual motion state quantity sensor are matched. There has been known a four-wheel steering system configured to control generated power of an electric motor or the like by means of (hereinafter referred to as "F / B control") (see Japanese Patent Application Laid-Open No. 5-155350).
[0003]
In a vehicle in which vehicle behavior is controlled by this type of F / B control, normal F / B control cannot be performed if a sensor for detecting an actual motion state quantity becomes abnormal. It is desirable from the viewpoint of fail-safe from the viewpoint of fail-safe that two sensors having different methods are used in combination to detect a certain amount of motion state, such as a transformer, and the outputs of the two sensors are compared to perform failure diagnosis of the sensors. However, the adoption of such a redundant system has a disadvantage of increasing the manufacturing cost.
[0004]
Therefore, it is conceivable to adopt a method of estimating a necessary motion state quantity from a signal of another sensor already provided by calculation, and comparing the estimated value with an actual value to diagnose a sensor failure.
[0005]
[Problems to be solved by the invention]
However, failures with clear causal relationships, such as output stoppage due to disconnection and chattering due to poor contact, can be diagnosed relatively easily and accurately. Is difficult to predict, and the accuracy of the estimated value is low, so that it is difficult to make a highly reliable diagnosis from the signal output state.
[0006]
In order to reduce the erroneous diagnosis, it is conceivable to increase the threshold value of the failure determination with respect to the difference between the estimated value and the actual value (hereinafter referred to as “error”) or to perform the diagnosis over a long time. The former has a higher probability of overlooking the failure, and the latter has a disadvantage that the control state which is not reliable must be continued during the failure diagnosis.
[0007]
The present invention has been improved so as to solve the problems of the prior art and to make it possible to reliably perform a failure diagnosis and not to affect the vehicle behavior during the failure diagnosis due to a sensor failure. It is an object of the present invention to provide a failure diagnosis method for a vehicle mobility control device.
[0008]
[Means for Solving the Problems]
In order to achieve such an object, according to the present invention, a failure diagnosis of a vehicle kinetic control device that performs F / B control of a vehicle behavior so that a detected value of an actual kinetic state amount and a model kinetic state amount coincide with each other. As a method, when the above error exceeds the threshold, it enters the fault diagnosis mode,
(1) Normal control continuation area for continuously performing F / B control,
(2) a decreasing control area for gradually decreasing the F / B control amount,
(3) Control stop area for stopping F / B control,
After that, the mode was changed to fail-safe mode.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 1 schematically shows an overall configuration of a four-wheel steering vehicle VC to which the present invention is applied. In FIG. 1, a steering shaft 2 having a steering wheel 1 fixed to one end is mechanically connected to a steering rod 4 of a front wheel steering device 3. Both ends of the steered rod 4 are connected via tie rods 7 to knuckle arms 6 supporting left and right front wheels 5 respectively.
[0011]
The rear wheel steering device 8 disposed on the rear axle side drives a steering rod 9 extending in the vehicle width direction by an electric motor 10. Both ends of the steering rod 9 are connected via tie rods 13 to knuckle arms 12 that support left and right rear wheels 11, similarly to the steering rod 4 on the front wheel 5 side.
[0012]
The front and rear steering devices 3 and 8 are provided with steering angle sensors 14 and 15 for detecting the positions of the steering rods 4 and 9 and detecting the steering amounts of the wheels 5 and 11. . The steering shaft 2 is provided with a steering angle sensor 16 for detecting a steering amount of the steering wheel 1. Further, a vehicle speed sensor 17 is provided for each of the wheels 5 and 11, a yaw rate sensor 18 is provided at an appropriate position on the vehicle body, and a brake operation sensor 19 is provided for the brake pedal.
[0013]
Each of these sensors 14 to 19 is electrically connected to a computer unit 20 that drives and controls the electric motor 10.
[0014]
In the four-wheel steering vehicle VC, when the driver steers the steering wheel 1, the steering rod 4 of the front wheel steering device 3 is mechanically driven, and the front wheels 5 are steered. At the same time, the amount of steering of the steering wheel 1 and the amount of movement of the steering rod 4 are input to the computer unit 20 via the respective steering angle sensors 14 and 16. Then, the computer unit 20 determines an optimal steering amount of the rear wheels 11 according to the traveling state of the vehicle VC obtained based on the input values of the front wheel steering angle, the vehicle speed, and the yaw rate. When driven, the rear wheels 11 are steered.
[0015]
FIG. 2 is a basic control block diagram of the vehicle mobility control device in the above-described four-wheel steering vehicle VC. The vehicle kinetic control device includes a model yaw rate calculation unit 21 that calculates an ideal yaw rate for the steering angle θ of the steering wheel 1 based on a preset function formula (or map), and a tire grip characteristic and a vehicle An F / F control unit 22 that outputs a feedforward (hereinafter referred to as F / F) control amount with respect to the steering angle θ based on a functional expression determined in consideration of response characteristics, and an actual yaw rate that is actually acting on the vehicle VC. An F / B control unit 23 that outputs an F / B control amount according to a deviation from the model yaw rate, and the rear wheel steering device 8 according to an added value of the F / F control amount and the F / B control amount. Is to be controlled.
[0016]
Next, processing related to the failure diagnosis of the yaw rate sensor 18 that detects the yaw rate as the actual motion state amount value will be described with reference to FIG. First, by multiplying the difference between the rotational speeds of the left and right driven wheels (the rear wheel 11 in the present embodiment) by a coefficient obtained in advance by an experiment, a motion state quantity estimated to be acting on the vehicle VC at the present time is obtained. Get estimated yaw rate as value. Next, the actual yaw rate acting on the vehicle VC is read from the output of the yaw rate sensor 18.
[0017]
In FIG. 3, the estimated yaw rate calculated by the calculation is compared with the actual yaw rate detected by the yaw rate sensor 18, and when the error between the two is below a predetermined threshold value, the sensor output is normal. F / B control is performed assuming that it is normal (normal control mode). When the error exceeds the threshold value, the control enters a normal control continuation region in which the normal F / B control is continued for a predetermined time predetermined in relation to the setting of the threshold value. In the normal control continuation area, the status of the occurrence of the error is monitored, and it is determined whether the error has occurred temporarily due to noise or the like or has occurred continuously.
[0018]
The relationship between the magnitude of the threshold value and the time of the normal control continuation area is set as shown in FIG. That is, if the threshold value is set low, the time in the normal control continuation region is lengthened, and if the threshold value is set high, the time in the normal control continuation region is shortened. Thus, when the error increases rapidly, the F / B control is immediately stopped to prevent a large change in the behavior, and when the error occurs slowly, the change in the behavior is small. By taking a long time, erroneous diagnosis can be prevented.
[0019]
If an error has occurred through the normal control continuation area, the control enters a reduction control area in which the F / B control is gradually reduced over a predetermined time.
[0020]
Then, when the failure is determined through the control stop area where the F / B control is completely stopped, the fail-safe mode is executed, the warning lamp is turned on, and the arithmetic unit is stopped.
[0021]
During this time, if the open-loop control (F / F control) according to the target value is continuously performed, the uncomfortable feeling given to the driver is compared to stopping the vehicle mobility control completely. Can be relaxed.
[0022]
【The invention's effect】
As described above, according to the present invention, since the state of the signal can be seen for a while in the normal control continuation region, erroneous diagnosis can be prevented by capturing instantaneous noise and the like. Even if the calculation accuracy of the estimating circuit is low and the error exceeds the threshold value for a longer time than in the normal control continuation region, fail-safe is executed immediately through the reduced control region. Since it is not performed, the time until the F / B control stops can be used for the diagnosis time. Therefore, a highly reliable failure diagnosis can be executed reliably and safely.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing the overall configuration of a four-wheel steering vehicle to which the present invention is applied.
FIG. 2 is a basic control block diagram of a vehicle mobility control device to which the present invention is applied.
FIG. 3 is an error diagram for explaining a failure diagnosis mode.
FIG. 4 is a relationship diagram showing the setting of a threshold value and a duration of a normal control continuation area.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Front wheel steering device 4 Steering rod 5 Front wheel 6 Knuckle arm 7 Tie rod 8 Rear wheel steering device 9 Steering rod 10 Electric motor 11 Rear wheel 12 Knuckle arm 13 Tie rod 14-16 Steering angle sensor 17 Vehicle speed Sensor 18 Yaw rate sensor 19 Brake operation sensor 20 Computer unit 21 Model yaw rate calculation unit 22 F / F control unit 23 F / B control unit

Claims (1)

A failure diagnosis method for a vehicle kinetic control device that feedback-controls a vehicle behavior so as to match a detected value of an actual motion state amount and a model motion state amount,
When the difference between the actual motion state quantity output by the sensor and the estimated motion state quantity obtained by the estimation calculation circuit exceeds a predetermined value, the apparatus enters the failure diagnosis mode, and at that time, a normal control continuation area for continuously performing feedback control. A failure control method for gradually reducing the feedback control amount and a control stop region for stopping the feedback control, and then shifting to the fail-safe mode, the failure diagnosis method for a vehicle kinetic control device.

Images